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Abstract

Hyperlipidemia is a major risk factor in etiology of cardiovascular disease. Previous
studies have shown association between vegetarian diet and low total serum cholesterol
as well as LDL-cholesterol which is a pointer to low risk of cardiovascular disease.
Dietary fiber, antioxidants and other classes of nutrients have been reported to ameliorate
cardiovascular risk factors. Fruits and vegetables being rich sources of fiber and
antioxidants have been the focus in intervention studies. The current work reports
the effect local fruits and vegetables on cardiovascular risk factors in African hypertensive
subjects in an 8 week study. Though there was no significant difference in the Body
Mass Index and HDL-cholesterol at the end of the eighth week, there were significant
reductions (P < 0.05) in serum triglycerides (125.87 ± 6.0 to108.27 ± 5.49 mgdL-1); total serum cholesterol (226.60 ± 6.15 to 179.20 ± 5.78) and LDL-cholesterol (135.69
± 5.56 to 93.07 ± 7.18 mgdL-1). We concluded that consumption of combination of local fruits and vegetables may
reduce the incidence of cardiovascular risk factors in Africans.

Introduction

Several epidemiological studies have implicated hypercholesterolemia and hypertriglyc
eridemia as major factors in the etiology of vascular disease [1,2]. Other prospective studies have equally shown that serum cholesterol [3], LDL-cholesterol [4], body mass index or obesity index, atherogenic index [5] and coronary risk index [6] are major risk factors in cardiovascular diseases.

Some studies have investigated the nutritional status of white and black American
vegetarians [7,8]. These authors reported lower serum total and low-density lipoprotein (LDL) as well
as cholesterol in vegetarians and suggested lower cardiovascular risk and essentially
lower blood pressure (BP)among vegetarians. Similar results were obtained with Native
African vegetarians [9].

Hypertension is a common cause of cardiovascular disorders and is essentially associated
with abnormal lipid and altered glucose metabolism [10,11]. Among the classes of food that have been taken to be beneficial in reducing risk
of cardiovascular disorders are fruits and vegetables due to their high level of fibres
[12], antioxidants [13] and complex carbohydrates [14].

Intervention studies of disease prevention with fruits or vegetables or both in Africans
are rare. It is important to determine if fruits and vegetables are associated with
lower BP and blood lipid and other risk factors for cardiovascular complications.

Materials and methods

Twenty hypertensive patients were randomly selected from the cardiovascular clinic
of Olabisi Onabanjo University Teaching Hospital (OOUTH). The subjects that had been
on diabetic drugs for over one year were educated on the purpose of the research work
and they all consented. The average nutrients intake by the subjects using estimated
food records were calculated.

Two weeks after the first table contact with the subjects, blood specimen were taken
and other parameters were measured for analysis to serve as baseline. Edible portion
of fairly ripe fruits (banana, pawpaw, grape fruits, tangerine and pineapple) were
diced mixed together in equal weight fruits salad with exception of banana which two
fingers were given per serving. Two servings of fruits salad (each measuring 100 g)
were given per day. Edible green leafy vegetable including fluted pumpkin leaf, spinach
and waterleaf were diced and given in 100 g portion per day after moderate cooking.
The supplementation of the normal diet of the hypertensive subjects with fruits and
vegetables was carried out for eight weeks after which it was stopped for two weeks.

Out of twenty subjects, only fifteen faithfully complied with the feeding regime and
this form the basis for the computation of results.

Analytical method

After the baseline measurements, the blood specimens were taken and parameters measured
at two weeks interval for a period of eight weeks. Blood Pressure values were extracted
from the patients' case notes. Triglycerides, total serum cholesterol and high-density
lipoprotein cholesterol (HDL cholesterol) concentration were determined by enzymatic
method using analytical kits. (Randox Laboratories U.S.A). While low density lipoprotein
(LDL cholesterol), was obtained by deduction. Atherogenic index (A.I) was calculated
using the formula of Abot

et al

[15] and coronary risk index (C.R.L.) was obtained by the method of Alladi

et al

[16]. Body mass index was calculated using the method of Garrow and Webster. [17].

Statistical analysis

The experimental design was completely randomized. The data were analyzed at 95% level
of significance using the two-tale Student's test.

Results

Table 1 shows estimated nutrient intake of subjects and the percentage difference between
the baseline values and the values in the presence of fruits and vegetables. Reduction
was noticed in intake of energy, sodium, fats and related compounds while increased
was observed in all other nutrients.

Table 2 shows Body mass index (BMI) and lipid profiles of the subjects. Significant differences
(P < 0.05) were noticed between the baseline values and the eighth-week values for
all the parameters except the BMI and HDL cholesterol. Also significant differences
(P < 0.05) was noticed between the eighth week values and the tenth week values in
Triacylgleride total serum cholesterol, however, no significance difference (P > 0.05)
was noticed in BMI and HDL cholesterol.

Table 3 shows a significant difference (P < 0.05) between the baseline values and the eighth-week
values in Atherogenic index and Systolic blood pressure while no significant difference
(P > 0.05) was between the eighth-week values and tenth-week values.

Discussion

Serum cholesterol is a major causative agent in the development of coronary heart
disease (CHD). Some studies have demonstrated a fall in total serum cholesterol resulting
from ingestion of soluble fibre [19,20] suggesting that high cereal fiber may protect against ischemic heart disease (IHD)
as well as high blood pressure, serum cholesterol and triglyceride levels. Our study
with daily intake of ≥ 3 times of different types of fruit and vegetables totaling
500 g for 8 weeks produced significant reduction in systolic blood pressure. The reduction
in the blood pressure might be due to significant high level of fibre. It has been
shown that African local fruits and vegetables are rich in dietary fibre, which has
been reported to have hypotensive and hypocholesterol effects [21]. Replacing animal products with vegetarian diets have shown reduction in blood pressure
in normotensive as well as hypertensive individuals [22,23]

In a large randomized controlled trial of diet and blood pressure that provided a
diet for 8 week that included 8.5 or 3.6 (control) servings of vegetables and fruit
daily, the participants who consumed the higher vegetable and fruit diet had a greater
reduction in systolic and diastolic than did the control subjects [24].

Elevated serum total cholesterol, LDL cholesterol concentration, are identified risk
factors for coronary artery disease [25,26]. However, in this study, we observed lower serum total cholesterol, LDL cholesterol
and triacylglycerol. These results may account for the significant reduction in BP
in our patients. A recent study has reported similar observation with 900 effects
of garlic may be due to inhibition of hepatic cholesterol biosynthesis [29].

In another study, [21,22] African local fruits and vegetables have been shown to be rich in dietary fibre,
which have been reported to have hypotensive and hypocholestrolemic effects. The plant
sterols have also been shown to produce a reduction of plasma low-density lipoprotein-cholesterol
and produced prolonged platelet aggregation after collagen epinephrine activation
(33).

AHA Medical/Scientific statement: The cholesterol fats: A summary of the evidence
relating dietary fats, serum cholesterol and coronary heart disease: A joint statement
of American Heart Association and its National Heart Lungs and Blood Institute

The Expert Panel. Summary of the second report of the National Cholestrol Education
Program (NCEP) Expert Panel on detention, evaluation and treatment of high blood cholesterol
in adults (Adult Treatment Panel II)